Electrical RC element

ABSTRACT

Electrical RC elements comprised of dielectric foils and electrically conductive layers which are arranged alternately to form a stack wherein at least one of the conductive layers is formed of a high-resistance material, such as a chromium-nickel alloy and alternate conductive layers are staggered in relation to each other with at least one of the conductive layers being end-contacted. In preferred embodiments, such stacked layers are wound into a coil structure and include at least two insulating foils to prevent short-circuiting.

0 Elite :11 Sttes atent 1191 1111 3,859,592 essler Jan. 7, 1975ELECTRICAL RC ELEMENT OTHER PUBLICATIONS [75] Inventor: g KesslerRegensburg Dommer Fixed & Variable Capacitors, McGraw Hill,

"many NY; 1960, p. 89. [73] Assignee: Siemans Aktiengesellschatt, Berlin&

Munich, Germany Primary Examiner-E. A. Goldberg Attorney, Agent, orFirm-Hill, Gross, Simpson, Van [22] Flled' May 1973 Santen, Steadman,Chiara & Simpson [21] Appl. No.: 357,008

[57] ABSTRACT [30] Fore'gn Apphcauon Prlomy Data Electrical RC elementscomprised of dielectric foils May 8, Germany and electrically conductivelayers are arranged alternately to form a stack wherein at least one ofthe U-S- onductive layers is formed of a high-resistance material uch asa chromium nickel aH y and alternate [58] Field of Search 333/79;317/2601256,261i conductive layers are staggered in relation to each323/781 77 other with at least one of the conductive layers beingend-contacted. In preferred embodiments, such References fined stackedlayers are wound into a coil structure and in- UNITED STATES PATENTSclude at least two insulating foils to prevent short- 2,126,915 8/1938Norton 317/256 X circuiting- 2,518,225 8/1950 Dorst..... 3,513,3685/1970 Boyer 317/260 x 17 27 D'awmg F'gures iuxiEi-i Eii W 3,859,592

sum 1 or 3 Fi i Fi .2 Fig.3

HIGH RESISTANCE LAYER HIGH RESISTANCE LAYER Fig.4 Fi .5 Fig.6

1 3 5 RRESISTANCE a i R K B D Fi .7 Fig.8 Fig.9

LRIYGEHR RESISTANCE A I g R R 1 3 A 1 Bi; 2 D

3 F'W E E PATENTEU 71975 3,859,592

- SHEET 2 OF 3 Fi .1o

HIGH RESISTANCE AYER Fig.13

HIGH RESISTANCE LAYER Fig.16

HIGH RESISTANCE LAYER 3 ELECTRICAL H thereof and' what is now consideredto be the best mode f contemplated for applying theseprinciples. Otherem- BACKGROUND oF Hei vENrioN 1. Field: of the invention. I r IThe'inve'ntion relates to electricalRCelernents (i.e. fart withou'tdeparting from the presentinven'tion and elements includingiat least oneresistor and at leastone spirit/and scope of the appendant claims. a

@equivalent' principles may be used and structural capacitor ll'l "astack, including high-resistance layers and dielectriefoils, whichma'y'carry low-resistance lay- BRIEF S R P ON O E DRAWiNGS ers) arrangedalternatelyone above the other. 410 FIGS. 1, 2 and 3.a r'e,respectively, a schematic side 2; Prior.Art'f elevational view, aschematic plan view and a circuit RC elements composed of a plurality ofresistance diagram'of an exemplary 'embodimentof the invention; andinsulating layers arranged alternately one above FIGS, .4, 5 and6areviews similar to those of FIGSL another are-known. A capacitive networkincluding a 1, 2 and 3, r espectively,of another exemplaryembodistarting capacitance made up of stacked conductive l5 ment of theinvention;

- coatings and dielectric layersisalso known wherein the FIGS. 7,8 and9are views similar to those of FIGS;

starting capacitance is divided up 'to' form a'desired net-[ 1-3,respectively, of yet anotherexempla'ryembodi V w work configuration byincisions which erttend at leastj ment of the invention;v r s r over theentire lwidthlof thearea of overlap of oppo- FIGS. 10, ll and l2are",views .;similar-1to those of sitely poled coatings. It is alsoknown to use a capaci- FIGS. 1, 2 and 3-, 'respectively, of a'furtherexemplary :tivenetwork of-this type as 'an'XYdnter'ference supembodimentof the.-invention f Y pression capacitorin layer constructions'I Insuchjs'up- FIGS.13, 14 and 15 areavi ev'vs imil r .w' h f.

' ,bodiments of the invention embodying the same or 5 changes rnay.be'm'ade as desired by those skilled in the pression ca'pacitt n s, thestarting capacitance is formed FIGS. 1-3, respectively,'of afurtherexemplary emas a layerc'o'ristr'uctio'n fromtwo' regions, withdifferent 'bodiment of the invention;

. types offcoating s and includi'ng an incision or cut froni' "FIGS. 16,17 and 18: are views similar to those of {one end face. 9

a s I FIGS. 1-3, respectively, ofanother exemplary embodi- Acolu'mnar-tnodule assembly oflayer'construction is. v ment of theinvention; i t

' also known wherein insulating layers are stacked atjn-' FIGS. 19, 20and 2l"'ar'e"views similar to those of .tervals one above another todivide capacitor electrode FIGSI 1+3, respectively, or; furtherexemplary emlayers from one another and currentis supplied at thebodiment'of the invention;

side face of thecolumnar body. l'n su'ch an arrange- FIGS. 22, 23 and 24are, respectively, a schematic ment, the. electricalconnection betweenindividual (side-sectional view, a schematic sideview, and ascheelectr'ode supply lines is effected in;' part 'by" low,;" "maticplanview of yet anotherekemplary'embodiment resistanceconductor pathsprovidedon the sidetface's t ofthe invention; and i or-by means ofelectrical resistance layers. ltjis' 'also 5 I1 FIGS'F'ZS, 26 and 27 areeach circuit diagrams of alknown toeffect electriccontactib'etween',stacked caternate uses of the exemplary embodimentsillustrated pacitor' electrodes by means of -metallizedfboresat-FlGSi22-24.

. stacked capacitor.

i ing distributed-1resistancesjand capacitance's'.

lt is a novel feature'jof' the invention to .through the insulatinglayers or by depositing electricalconductorpaths and resistances on theupper'face'ofca M Y-' HE INVENTION j alternately'ss o-as to form astacktwhereinat least one of f The-inventionprevide's anelectrical'.RC-elerne nt'havjf the' jc ondi ctivelayers is ahigh-resistance layer and al-' ternate'cenvductivetlayers are staggeredwith respect to.'-

...one '2i riother"and;a t least one condqctive layer (or a set eat jelectricalfRC element comprised of inslilating feilfsarjd fofcondiictive layers) is end-contac'ted.'

stack, with atleast one ofthe conductivelayers'ineludaingfa'hi'gh-resistancelmaterial and altern'atecoridtictive'layers'being" staggered ,with 'respect to oneganother and very compact.RC elements which areeasily-' masselectrically'condnctiveklaye'rsarranged alternately-in. lneertain preferredembodiments, stacked layers are T [wound intoia'coil, similar to a woundcapacitor and include, of eourse atleast two insulating foils'to preventI "short cir'lciiitingQ I at'Jeast-one-fof'the";condnctivelayerstbeingfen I contacted. I .I

. and ar'e readily mass-produced. The chargeand dislt isanother, novelfeature of the inventionj'toprovide charge characteristics of the RCcombination may be selectedQ'within ,wide parameters and 'the electricalproduced: Thecliarged and-discharge characteristiesof 5 initialormasterstacklis completed by providing inei-j l sions and appropriatelyselecting the 'numberand sions in the" stack and lay-selecting thenumberand flength ofincisions used. The RC ratio is determined infoilsused therein. f Z

dependently offurtherprocessing of an RC element, by;

length of such incisionsjThe RC ratio is deterrn'inedin- H y 'the'p'rper selection of conductive layers and dielectrican initial selection ofconductive layers and dielectric jxyfoilszf Other and further featuresofthe present invention willbe apparent from the following descriptionand-3' 5 claims and are illustrated in theaccompanying'drawbymetallizinjgor coating one or both sides of syntheticresirifoil strips-in a coriventional manner. Inembodi- S DESCRIRTION OFPREFERRED EMBODIMENTS 4 Tbe'invention provides RC elementsformed ofinsu- *latihg foilsa'ndelectrically conductive layers arranged TheRCeleme'nts of the invention arevery 'compact I I k characteristics: maybe varied or compensated. even i such RCelemenIts may be varied oradjusted after the -after the initialstack has been completed, withineidependently of further processing of the RCelemen't by :4

The RC elements of the invention maybe prodnced 'menlts' whe'relow-resistance layers are utilizedfthey' ings which, by way ofillustration, show preferred em shou'ldpossessa surface resistance onthe order o'fmag-f bodiments of the present invention and the principlesnitude of IQ/square and such layers may-advanta- I geously be composedofaluminumfjHigh-resistance I lOMQ/square and ma yqbecomposedlofachromium- E nickel alloy, of a high-resistance metal oxide, such as forl'xa'mple indium-o'x i'defor o f arbon ln certain embodim'ents, theconductive. layers may be, composedof-j layers of syntheticresinrriate'rialwhichdi'r'ectly conduct electrical current, i.e.syntheticiresinffoils which have been rendered electrically"conductiveembedding metal particles therein.

Coatings on the, nsulating or dielectric foils can be;

. faces sufficientlytocause the end contacted layersof layers shouldpossess a surfaceresistanceon the order 10f magnitude -r angi ng ffromlOQ/squar'e to'above' "the'various individual layer sequences toremain-elect'rically isolatedfrom one another (i.e., t he so-calledlongitudinal isolation). This arrangement provides three or moreconnection possibilitiesfor an external current supply and embodimentsutilizing suchan arrangement may be produced as four-pole, six-pole,etc.

elements." 3

The individual-RC elements may be subsequently l0 split-offfrom (e;g.,sawn away from) theinitial or masdivided up into'a plurality ofsubsidiary'coatings in a conventionalmanner by uncoated longitudinalstri'p's'.

AltEI'IIatiVelyJlhE'fOilS themselves may be divided into separate stripsan'dfspaced apart from each other at a sufficient distance for theintended function, especially Where the conductive layers are'foilshaving an inherent conductivity. Further, the coatings can be made ofallow-resistance at the lateral edges provided for contacting, such asby reinforcingthe coating and/or by the applicationof an auxiliarylow-resistance layer, that ,satisfa'ctory end-contacting isreadilyattainable. This concept is especially advantageous with jfoilshaving x tance coatings;

The conductive coatings in indiv idual planes of a 1 mar stack, which isproduced 'irithe form of long strips or ringsgwith the length of'the cutfunctioning in a known manner to determine the-capacitance orresistanceof'the element. The RC elements may be further alteredfby'incisions which begin at-o n'e end contact facea'nd terminate priorto'the other end contact face. Basic'a]ly,stich incisionsf ronioneend-face provide parallel connections whilei ncisi onsfromboth end facesprovide series 'connec'tio ns' Depending on the desired 'RC combinationanj incision may'extend overtheentire width o'f-t hfe ,0. erlap area ofoppositeUPOled coatings or it may bfe s'hofrtr'than the overlap area.

The RC'ele'men {of invention. ample," as sparkequenc'hingvelemen l1.stack arepreferably not all connected to external terminalsi Tliisarrangement providesafseries connection .an'djp v y Lcrease-1infdieIQCtricstrength The conductive, c oat ingsf rnindi v v"may be conventional'ly connec ted to external terminals 1 at 'severalpoiint'sglf these terniinals are connec'te'd-tofor .:carry differentpotentials Ian, 1 ctricresistance is 'at- 35 ftainedfhetweenf th'e'j twoterrnina ifthe term inals'carrytheisamep entialf a change "in*isatt-ained The. insulating foilsand" conduct ve layer Yb stacked in a:constantly repetitive sequence within an -overall' RCjQ-elenienFhisfi's'gthesofcalled simple co structionqf-lioweyerg..-a'pluralityiofdifferentlay" I quences' mayf'alsobe advantageously stackedon ove anotherfthis is the 'so-c;'1l ljed. multipleconstruction; -I*multiple "con structions',-additional;insulating foils may ."beincludedbetweenfindividual layer sequenceslin' order to provide 'aspecific-insulation path;

Electrical isolation-of individual layer sequences is; I achieved,u'even after end-contacting by'. means of the I Schooprprocess hasbeenyeffected, by. embedding insulatingfoils between .the'individuallayer, sequences so that such additional foils project at one ;or:,b0th',end

bffcapa'ci'tance a't' various planes between one another rovides-areduction in capacitive value and-an in 3 stack plane's" 'the' fi'r s thigha'resistance "coating 1 L;1""Th e" electrica contact Bis connectedto. resistance R' j forl-rned by the age-divider's as switchingnetworksbetween"amplifier stages, as RC t'r .elementsfetc.

' Referringnow to th 0 RC element which can be producedlin the .mannerof] resistance coating lian'd.a-se'condghigh cSistanceicoat: 1

ing'2 areapplied on.therespectivesidesofan'insulating foil-.3.Thecoatings land 2 are st'agg er edgin 're'spe'c tto, e l effec ted.-"

one another to enable send-contacting; withoutf causing a short circuitj FIGJ Z shows a plan viewof the el'ernen .FIG. 1.: The firstcoatinglforrn'scoa't'ing 2 forms a conta "ridi-cated-byfreferencel numeral :4 i,i FlG." 3 shows the: equivalent electrical rcui-t 0f the elementshowjnfatFIGS. l and 2i T-lle onta'ctz'Ai i'sconne'ctedw'ith a resistanceRijfo'rm'ed b e'c'dnd hjgh''resista'nce coat ng "2. A dis'trijbutedcapjaci orK is arranged'betweenthe.two resistor'suRi' and R .Th;egh-resistanceco'ating's11{and 2 may. be-fbfr'hed fo rexampleof'achrornium-nickelalloy, of iridiunifogr i-dc?'of'-tin"-'oxide,ofcarbon or of any other ui't a .h' esist ce"material.

6* 6 .(FIG. 5") extending crosswise-parsho'wa .ftirth er 'ernbodiment'oflfthe inve'n ansit time' elements, as phase-rotation nthembodimentillustrated at EIGs .-4-6, a pa or nslulati ngffo'ils 3;a r'e,respectively, coated on one' si e hefeof withl a. high-resistancecoating landwith -a b es tance cOatingSarid are-stackedinja'staggeredrelarespect: mjoneanom r as shown. Alt otal of fourfcQntact-terniinals',- A, B,.C and D, are attaine'dbyQmejansn t o he-st'ack' fsrom the two respectiveend faces o'w' 'a't FlGrfiyafour-poleelerheht is th'ujs c l resistance Rjjand a distributedcan'su'lat'ing foils 3 are, respectively." el-thereo'f; with ahigh-resistance coat" d 6"are' saw t ansversely'int'o' an element soformed from one end face. The center incision 7 extends through theentire overlap area of the oppositely poled coatings while the othercuts 6, 6 do not. This arrangement provides a total of five contactterminals A, B, C, D and E and, as'shown at FIG. 9, provides two RCfour-pole elements, consisting of the resistors and capacitors R K and RK and a single common ground line.

In the embodiments of the invention illustrated at FIGS. to 12, theupper insulating foil 3 is completely covered on one side with ahigh-resistance coating 8 and the other side of foil 3 is partiallycovered with an insulating foil 9, which is thicker than foil 3. Aninsulating foil 16, metallized on both sides thereof with lowresistancecoatings 10 and 2, is arranged so that coating 10 contacts foil 9. Asecond relatively thick insulating foil 9 is provided in contact withcoating 2. As shown at FIG. 11, two incisions 7, 7 are provided fromopposite end faces and extend through the entire overlap area of theoppositely poled coatings to provide four external connections, A, B, Cand D. As shown in FIG. 12, such an arrangement produces a seriesconnection of three resistors, R,, R and R which are in each caseshunted by a capacitor K K and K respectively. This type of element maybe used, for example, as a frequency-compensated voltage-divider. Anadvantage of this embodiment includes the fact that as a result of thepre-selection of conductive coatings and insulating foils, the RC ratiois constant for all resistance values. Therefore, the position of theincisions may be determined exactly in accordance with a desiredvoltagedivider ratio and the correct value of the compensationcapacitance K will always be automatically obtained.

Another embodiment of a compensated voltagedivider is shown at FIGS.13-45. In this embodiment, the element is constructed from two differentlayer regions. A first layer region is formed of an insulating foil 3which is completely covered on one side thereof with a high-resistancecoating 8 and partially covered on the other side by an intermediateinsulating foil 11. A second layer region is formed of two insulatingfoils 3, each coated on one side thereof with a low-resistance coating 5and 10. It will be noted that coatings 5 and 10 are arranged instaggered relation to one another. As shown at FIG. 14, tworeciprocalcuts or incisions 7, 7 are provided and extend crosswise fromopposite end faces over the entire overlap area of the oppositely poledcoatings. As best seen at FIG. 15, this forms a series connection ofthree resistors R R and R which are shunted with the aid of capacitors KK and K An embodiment of a RC element having low-pass characteristics isillustrated at FIGS. 16-18. A foil 3 of an insulating material is coatedon one side with a highresistance coating I and an uncoated intermediatefoil 11 is placed on the other side of foil 3 so as to form a firstlayer zone. A second layer zone is formed by two insulating foils 3,each of which are coated on one side with a low-resistance coating 5 and10 respectively. It will be noted that coatings 1 and 10 are arranged sothat they both can be contacted at the same end face and that these twocoatings are of different widths. A single incision 12, best seen atFIG. 17, extends from one end face transversely into the formed stackand is longer than the width of coating 10 but shorter than the width ofcoating 1. This arrangement provides three terminals, A, B and C, andresults in the equivalent circuit diagram shown at FIG. 18.

FIGS. 19-21 illustrate an embodiment having a highpass characteristic. Afirst layer zone is formed of an insulating foil 3 which has onecomplete side thereof coated with a high-resistance coating 8 and, alongthe other side, has an intermediate foil 11. A second layer zone isformed by a first insulating foil 3 having a lowresistance coating 10 onone side thereof and a second insulating foil 3 having a low resistancecoating 13 on a similar side thereof. It will be noted that coating 13is so arranged that it cannot be contacted at either of the end faces.An incision 12 is provided to extend from one end face for a distancegreater than the width of coating 10 but less than the width of coating13. This arrangement produces three electrical connecting points, A, Band C, and results in the high-pass filter diagrammatically shown atFIG.21.

FIGS. 22 through 27 illustrate further exemplary embodiments of RCelements in accordance with the principles of the invention. Two layerzones are separated from one another by an insulating foil 14, whichprojects on one side beyond that end face and thus provides individualelectric contacts at such face. A first layer zone is formed by aninsulating foil 3, one side of which is completely covered with ahigh-resistance coating 8 and the other side of which is partiallycovered with an intermediate foil 11. Below the projecting insulatingfoil 14, two further insulating foils 3 are stacked, each of which arecoated on one side thereof with a low-resistance coating 10 and 5respectively, which are in staggered relation to one another. FIG. 23illustrates a side view of the stack produced in this manner. Theseparation foil 14 which projects on the right, beyond the end face andthe end 15 of an incision 7 are shown at FIG. 24. Above the separationfoil 14, on the right-hand side of FIG. 24, terminals A and B result andbelow foil 14, terminals C and D result. On the lefthand side of thiselement, a common ground terminal E is provided. As best seen in FIG.24, an incision 7 is provided and extends transversely over the entireoverlap area of the oppositely poled coatings. FIGS. 25, 26 and 27illustrate equivalent circuit diagrams attainable with the element shownat FIGS. 2224. Depending upon the wiring of the individual terminals .A,B, C and D, one may attain either two resistors R and R and twocapacitors K, and K which are connected to a common ground line B, asbest seen in FIG. 25, or as shown at FIG. 26, a four-pole havinglow-pass characteristics, or as shown at FIG. 27, a four-pole havinghigh-pass characteristics.

It will be appreciated that starting from a standard initial or masterRC element of the invention, it is possible to produce different typesof RC combinations, such as two-poles, four-poles, six-poles, etc. bysuitable application and combination of the disclosed principles of theinvention. Further, each layer zone need not be limited to only twooppositely poled coatings as suggested by the drawings; it is possible,in fact, to provide a plurality of correspondingly parallel connectedcoatings in order to increase the capacitance of a select element.

Further modifications, variations and alterations may readily occur tothose skilled in the art and it will be understood that these may beeffected without departing from the spirit and scope of the novelconcepts of the invention.

I claim as my invention:

v 1. An electrical RC element comprising a plurality of insulatingfoils, at least two of which are provided with an electricallyconductive layer on a face thereof, said foils and layers being arrangedalternately to form a stack, at least one pair of adjacent conductivelayers having at least one insulating foil therebetween, at least one ofsaid conductive,- layers being a' high-resistance layer and at leastoneof said conductive layers being a low-resistance layer, with only oneconductive layer being disposed on a respective foil, and alternateconductive layers staggered with respect to one another, said stackhaving at least one transverse incision therein extending from one endface of the stack in all layers and foils thereof, and at least saidconductive layer of high resistance being positioned for end contactwith an external current source.

2. An element as defined in claim 1 wherein some of said conductivelayers are formed of aluminum.

3. An element as defined in claim 1 wherein said high-resistance layeris formed of a chromium-nickel alloy.

4. An element as defined in claim 1 wherein said high-resistance layeris formed of a high-resistance metal oxide.

5. An element as defined in claim 1 wherein said high-resistance layeris formed of carbon.

6. An element as defined in claim 1 wherein some of said conductivelayers are formed of an electrically conductive foil of synthetic resinmaterial.

7. An element as defined in claim 1 wherein said conductive layers areeach divided up into a plurality of laterally disposed sublayersmutually insulated from one another.

8. An element as defined inclaim '1 wherein only some of said conductivelayers are connected to'an external current source;

9. An element as defined in claim 1 wherein at least some of saidconductive layers are each connected to an external current source at aplurality of points.

10. An elementas defined in claim 1 .wherein said stack includesadditional insulating foils.

11. An element as defined in claim 1 wherein at least one insulatingfoil extends beyond at leastone end face of the stack. g

12. An element as defined in claim 1 wherein said stack includes aplurality of similar stacked layer sequences.

13. An element as defined in claim 1 wherein said stack includes atleast two different stacked layer sequences.

14. An element as defined in claim 1 wherein said transverse incisionextends over the entire width of the overlap area between oppositelypoled conductive layers.

15. An element as defined in claim 1 wherein said stack includes atleast one transverse incision extending from each end face thereof.

16. An element as defined in claim 1, wherein said element comprises atleast three conductive layers,

forming at least two such pairs of adjacent conductive layers.

17. An element as defined in claim 1, wherein a conductive layerpositioned for end contacting is low ohmic and is common to a pluralityof RC components forming the element.

1. An electrical RC element comprising a plurality of insulating foils,at least two of which are provided with an electrically conductive layeron a face thereof, said foils and layers being arranged alternately toform a stack, at least one pair of adjacent conductive layers having atleast one insulating foil therebetween, at least one of said conductivelayers being a high-resistance layer and at least one of said conductivelayers being a low-resistance layer, with only one conductive layerbeing disposed on a respective foil, and alternate conductive layersstaggered with respect to one another, said stack having at least onetransverse incision therein extending from one end face of the stack inall layers and foils thereof, and at least said conductive layer of highresistance being positioned for end contact with an external currentsource.
 2. An element as defined in claim 1 wherein some of saidconductive layers are formed of aluminum.
 3. An element as defined inclaim 1 wherein said high-resistance layer is formed of achromium-nickel alloy.
 4. An element as defined in claim 1 wherein saidhigh-resistance layer is formed of a high-resistance metal oxide.
 5. Anelement as defined in claim 1 wherein said high-resistance layer isformed of carbon.
 6. An element as defined in claim 1 wherein some ofsaid conductive layers are formed of an electrically conductive foil ofsynthetic resin material.
 7. An element as defined in claim 1 whereinsaid conductive layers are each divided up into a plurality of laterallydisposed sublayers mutually insulated from one another.
 8. An element asdefined in claim 1 wherein only some of said conductive layers areconnected to an external current source.
 9. An element as defined inclaim 1 wherein at least some of said conductive layers are eachconnected to an external current source at a plurality of points.
 10. Anelement as defined in claim 1 wherein said stack includes additionalinsulating foils.
 11. An element as defined in claim 1 wherein at leastone insulating foil extends beyond at least one end face of the stack.12. An element as defined in claim 1 wherein said stack includes aplurality of similar stacked layer sequences.
 13. An element as definedin claim 1 wherein said stack includes at least two different stackedlayer sequences.
 14. An element as defined in claim 1 wherein saidtransverse incision extends over the entire width of the overlap areabetween oppositely poled conductive layers.
 15. An element as defined inclaim 1 wherein said stack includes at least one transverse incisionextending from each end face thereof.
 16. An element as defined in claim1, wherein said element comprises at least three conductive layers,forming at least two such pairs of adjacent conductive layers.
 17. Anelement as defined in claim 1, wherein a conductive layer positioned forend contacting is low ohmic and is common to a plurality of RCcomponents forming the element.